Continuous extraction press

ABSTRACT

Two conveyors form therebetween a pressure zone which tapers in the common direction of conveyor movement. At least one of the conveyor belts consists of hingedly connected plates which are backed by a row of rollers spaced more closely than the length of each conveyor plate. The material to be extracted is fed into the pressure zone in a continuous loop of a porous web folded into a U-channel while in the pressure zone.

United States Patent Inventor Oskar Braun v fBensheim, Bergstrasse, Germany Appl. No. 798,758 Filed Feb. 12, 1969 Patented Dec. 7, 1971 Assignee Josef Willmes KG Bensheim Bergstn, Germany Priorities Feb. 16, 1968 Germany Dec. 19, 1968, Germany, No. P 18 15 593.6

CONTINUOUS EXTRACTION PRESS 14 Claims, 21 Drawing Figs.

US. Cl 100/119, 100/ 153 int. Cl B30b 9/24 FieldofSearch ..100/l51-154, I 1 18-120 [56] References Cited UNITED STATES PATENTS 258,349 5/1882 100/120 X 271,387 1/1883 100/120X 1,702,085 2/1929 100/1 19 X 1,764,456 6/1930 100/118 X 3,453,951 7/1969 100/118 Primary Examiner-Peter Feldman Altorney- Kurt Kelman ABSTRACT: Two conveyors form therebetween a pressure zone which tapers in the common direction ofconveyor movement. At least one of the conveyor belts consists of hingedly connected plates which are backed by a row of rollers spaced more closely than the length of each conveyor plate. The material to be extracted is fed into the pressure zone in a continuous loop ofa porous web folded into a Uchannel while in the pressure zone.

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05mm BMW SHEET USUF 10 PATENTEU E 7|97l 3,625,141 SHEET DEUF 10 nvnwrak 65 MAR ERA (1N PATENTED DEC 7 I971 SHEET MW 10 lure-Mm) Mm RAUN PATENTED [15c 719m sum 08 or 10 l/VIIN raw 0 KM EMU V Mew CONTINUOUS EXTRACTION PRESS BACKGROUND OF THE INVENTION This invention relates to the extraction of liquid from liquidbearing solids, and will be described hereinafter in its application to the extraction of juice from mashed fruit.

It is common practice to extract juice from mashed fruit in pot presses in which the mashed material is confined between porous webs while being subjected to pressure. It is known that juice is extracted most rapidly if applied pressure is initially low and is gradually but continuously increased. The layer of mash between the layers of enveloping porous web should be relatively thin to facilitate release of the juice and to permit the operation to be completed without requiring an intermittent loosening of the compacted material. The web material must be chosen to prevent coarse particles of mash from being discharged with the juice even at very high ultimate pressure.

It has not been possible heretofore to extract juice from fruit mash under the known optimum conditions in a continuous operation which does not normally require the intervention of a human operator. It has been proposed heretofore to confine the mash between endless loops of filter cloth or perforated metal foil while the filter medium with the confined mash is passed between pressure rollers. This arrangement does not permit the pressure to be increased continuously during passage of the mash through the extraction zone because the filter cloth or metal foil sag between consecutive pressure rollers. The applied pressure fluctuates, and the extracted mash, therefore, still contains significant amounts of juice which could be recovered in a platen or pot press. Retention of juice is favored by the relatively great angle at which the walls of the pressure zone converge ahead of each pair of pressure rollers, thereby locking juice between compacted and relatively impenneable walls of extracted mash material.

The primary object of the invention is the provision of a continuous extraction press which permits mashed fruit to be extracted under the known optimum conditions described above with an efficiency substantially as high as that available from platen or pot presses, and without the need for human labor which accounts for most of the cost of operating the known batch presses.

SUMMARY OF THE INVENTION The press of the invention employs two conveyors between which the mash is extracted, as in the aforedescribed known arrangement. However, at least one of the two conveyors is a plate conveyor whose plate members are connected into a closed loop by hinges and are guided by a row of backing rollers while their front surfaces are directed toward the pressure zone. The length of each plate member in the common direction of movement of the two conveyors is at least equal to the spacing of the backing rollers in the row so that the front surfaces of the plate members form a continuous wall of the pressure zone. The pressure zone decreases in width continuously in the direction of conveyor movement. Layers of porous, pliable web material are superposed on the two endless conveyor faces for movement through the pressure zone with the same.

Other features, additional objects, and many of the attendant advantages of this invention will readily become apparent from the following detailed description of preferred embodiments when considered in connection with the appended drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 shows and extraction press of the invention in side elevational section on line I-I in FIG. 2;

FIG. 2 is a plan view of the press of FIG. 1;

FIG. 3 illustrates the press of FIG. 2 in front elevational section on line III-III;

FIG. 4 shows a detail of the apparatus of FIG. 3 on a larger scale;

FIG. 5 illustrates a variation of the device of FIG. 4;

FIG. 6 shows a detail of the apparatus in a view corresponding to that of FIG. 2, but on a larger scale;

FIG. 7 shows a modified detail for use in the apparatus of FIG. 1 in elevation;

FIG. 8 is a fragmentary, side elevational view of a modified press of the invention;

FIG. 9 shows the device of FIG. 8 in plan section on the line IX-IX;

FIG. 10 shows yet another variation of the device of FIG. 4 in plan view,

FIGS. 11a to 11d illustrate an element of the press of FIG. 1 and three modifications thereof in respective front elevational sections;

FIG. 12 shows a modified press in a fragmentary view corresponding to that of FIG. 2, but on a larger scale;

FIGS. 13a to 13c respectively illustrate an element of the apparatus of FIG. 3 and modifications thereof in views corresponding to that of FIG. 3;

FIG. 14 shows another press of the invention in fragmentary side elevation,

FIG. 15 illustrates an additional press in plan view; and

FIG. 16 shows the apparatus of FIG. 15 in elevational section on the line XVI-XVI in FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring initially to FIGS. 1 to 3, there is seen as extraction press of the invention whose operating elements mainly consist of two plate conveyors l. The conveyors are supported on a skeleton frame consisting of four horizontal steel channels 2 connected by two rectangular frames consisting of upright channels 3 and transverse channels 4. The frame is fixedly fastened to a heavy foundation, not shown.

Extension arms 5 at the ends of the horizontal channels 2 carry bearings for the driven shafts of paired discs 6. The arms 5 at the rear ends of the channels 2 are fixed whereas the front arms 5 may be shifted longitudinally of the channels 2 by means of adjusting screws 7. Six pins 9 project from each disc 6 toward the other disc on the same shaft, and the pairs of discs 6 are attached to the common shaft in such a manner that the pins 9 are longitudinally or axially aligned. The belt of each conveyor 1 consists basically of steel plates 8 connected by hinges 10 in a closed loop trained over the pins 9 between a pair of discs 6 at the front end and a pair of discs at the rear end of the press. The screws 7 are set to maintain the desired tension in the conveyors. The six pins 9 eqiangularly distributed about the circumference of each disc 6 are spaced apart by the uniform length of each plate 8, and the pins between the discs 6. The upright shafts of the discs 6 are driven at the same speed in a conventional manner, not explicitly illustrated, but evident from the description of FIG. I6 hereinbelow.

The plates 8 of conveyor I extend in a common plane in the conveyor strand which is closely adjacent a corresponding strand of the other conveyor. While the two strands extend in a common direction, and move in that direction when the discs 6 are rotated, they converge somewhat from the front toward the rear of the press. As is better seen in FIG. 6, the several plates 8 in the two conveyor strands which bound the pressure zone 11 of the press therebetween, are impervious to liquid. The plates 8 are covered with stainless steel sheets 12 which are attached to the plates by means of stainless steel screws 14 and project beyond the leading and trailing transverse edges of each plate 8. The portion of the sheet 12 which projects beyond the leading plate edge is bent into a U-fold or bead 15. The rearwardly projecting cover portion retains a resilient gasket 13 which sealingly engages the bead IS on the subsequent plate 8. The stainless steel sheets protect the steel plates 8 against corrosion by acid in the fruit juice. Since the sheets 12 form the front surface of the conveyor 1 in the pressure zone 11, a gap opens between the bead l5 and the gasket 13 while the associated hinge 10 travels over the pins 9 on the discs 6.

Reverting now to FIGS. I to 3, each conveyor 1 is supported on rollers 16 outside the pressure zone and is backed in the pressure zone 11 by rollers 19 arranged in a straight row. The rows converge slightly from the front toward the rear to provide the aforedescribed tapering shape of the pressure zone 11. The center-to-center spacing of the rollers 19 within each row is somewhat shorter than the length of the plates 8 in the direction of conveyor movement so that each plate 8 is always backed by at least one roller 19, and the planar alignment of the plates in the pressure zone 11 is maintained. The backing rollers 19 are even more closely spaced near the rear end of the pressure zone to prevent bending of the plates 8 between adjacent rollers under the prevailing relatively high pressure.

The width of the pressure zone 11 may be adjusted according to the nature of the mash being extracted, as is best seen in FIG. 4. The two ends of each roller 19 are joumaled in respective bearing brackets 20 slidable inward and outward of the pressure zone 11 transversely to the direction of conveyor movement in corresponding recesses of the channels 2. Adjusting screws 21 threadedly engage the channels and abut against the brackets 20 to move the rollers 19 inwardly of the pressure zone. The brackets are normally held against the screws 21 by the pressure of the conveyor plates whose rear surfaces are engaged by the rollers 19.

A wedge-shaped entrance 22 to the pressure zone 11 is defined by two heavy metal plates 49 fixedly mounted on the conveyor frame in a manner not further illustrated. They guide a continuous loop of a web 23 into the pressure zone. The two longitudinal edges of the web, which may consist of filter canvas, synthetic woven, knitted, or nonwoven fabric, or of metal mesh, as is known in itself, are attached to respective carrier and guide chains 24 by means of hooks or eyelets 25. The chains 24 travel over guide pulleys in such a manner that the web 23 is folded into a U-channel or through 28, best seen in FIG. 3, before entering the pressure zone 11, and is flattened out after leaving the zone.

The paths of the two chains 24 thus diverge outwardly of the pressure zone 11 in both opposite directions. While the web 23 is in the pressure zone, the associated chain portions move in slotted guide tubes 29 along the upper edge of the zone and to a first pair of pulleys 26 at the rear end of the zone. The chains then diverge toward reversing pulleys 26', and extend downward and forward from the same to pulleys 26" which are spaced apart the full width of the web 23, thereby completing the unfolding operation.

The flat web 23 travels forward under the conveyors 1 toward a set of folding pulleys arranged symmetrically to the aforedescribed pulleys 26, 26', 26". Pulleys 27" are lowermost and farthest apart. The higher, more closely spaced pulleys 27 reverse the direction of chain movement to the closely juxtaposed pulleys 27 at the entrance 22 to the pressure zone I 1.

During normal operation of the illustrated press, fruit mash is fed to the partly folded web 23 in the entrance zone 22 between the plates 49 by an automatic feeding mechanism, conventional in itself, of which only a sensing element 30 is seen. The sensing element is the float of a switch which remains closed until the mash in the entrance zone 22 reaches a desired level. When the float rises sufiiciently to open the switch, the feeding mechanism is stopped until the float drops again. The pressure zone is thus supplied with mash at a reasonably uniform rate. The frictional engagement of the web 23 with the plates 8 or their covers 12 under the weight of the mash in the web channel is sufficient to draw the web with the mash confined therein into the pressure zone. As the walls of the zone gradually converge on the mesh, juice is extracted from the same at a rate which can be controlled by setting the screws 21. Under the optimum conditions, which must be determined experimentally for each type of mash, as in the operation of a batch press, the material ultimately released from the unfolding web 23 at the discharge end of the zone 11 contains no more juice than the extracted material obtained from a competently operated batch press.

The extracted juice flows along the impervious covers 12 of the plates 8 in the pressure zone 11 between the yarns or wires of the web 23 downward into a gutter 31. The web 23, while returning to the entrance zone 22 is practically planar configuration, is cleaned of adhering pulp by a rotary brush 32, by a rotating shaking plate 33, and by water discharged from spray nozzles 34.

Numerous variations and modifications may be made in the apparatus described above without basically changing its mode of operation nor the results achieved, and such modifications may be convenient or necessary when extracting certain types of fruit or mash having specific physical or mechanical properties.

When the mash supplied to the press may accidentally contain hard pits, it is desirable to provide the backing rollers 19 with resilient abutments as shown in FIG. 5 to replace the adjusting screws 21. Cup springs 55 are arranged in recesses of the channels 2 behind the bearing brackets 20, and threadedly mounted plugs 56 permit the positions of the relaxed springs 55 to be adjusted for the normal setting of the backing rollers 19. Damage to the apparatus, and particularly to the web 23, is less likely to be caused by a hard pit or the like when the rollers 19 can yield under the suddenly increased pressure. Yet, optimum extraction conditions are restored as soon as the pit has passed each roller.

If a press is used for extracting batches of fruit which difier v in consistency or moisture content, but are otherwise closely similar, the necessary adjustment of the backing rollers 19 is facilitated by the modified arrangement seen in FIG. 10 in which a wedge-shaped rod 57 extends along each row of rollers 19 in camming engagement with the bearing brackets 20. The wide end of the rod 57 projects from the press at the discharge end of the same, and provides a handle by means of which the rod 57 may be moved longitudinally for simultaneous displacement of all the rollers 19 in one row inward or outward of the pressure zone.

The illustrated rod 57 has a planar cam face so that the inclination of the row of backing rollers relative to the median plane of the pressure zone 11 remains unchanged when the rod is shifted, but other arrangements are obviously possible. Cams other than the wedge-shaped rod 57 may be employed for the same purpose, and the use of a series of rotary cams mounted on a common shaft and engaging respective bearing brackets 20 for shifting the same in an obvious manner when the cams are turned is specifically contemplated.

As is shown in FIG. 110, the plates 8 are rectangular in section perpendicular to the normal direction of conveyor movement. Some types of mash tend to settle in the trough or channel 28 formed by the web 23 in the pressure zone 11, others tend to overflow from the open top, and yet others may both settle and overflow. They may be confined more firmly in the channel 28 by changing the configuration of the conveyor plates so that the width of the pressure zone 11 is not uniform in plane perpendicular to the direction of conveyor movement. Thus the plates 8' shown in FIG. 1 lb flare in an upward direction to urge the mash downward, The identical plates 8' seen in FIG. 1 1c in a reversed position, are helpful in preventing settling by pushing the mash upward in the channel 28. Ultimately, the plates 8" illustrated in FIG. 11b have a front surface which is concavely arcuate about an axis extending in the direction of conveyor travel to hold the mash near the center of the trough or channel 28.

If overflowing of the mash from the pressure zone 1 I cannot be controlled by modifying the configuration of the conveyor plates, the trough or channel 28 may be closed in an upward direction. As illustrated in FIG. 13a, the longitudinal edges of the web 23 are provided with resilient beads 58 which sealingly engage each other when the web 23 is folded into the trough or channel 28. The beads may consist of the same material as the remainder of the web, rolled to thicken the edge, or of affixed other resilient material, such as rubber.

In the modified arrangement seen in FIG. 13b, a flap 59 of pliable fabric of similar material is fastened to one longitudinal edge of the web 23, and is lifted by a nonillustrated guide at the entrance zone 22 to close the open side of the U-shape.

Ultimately, a separate, closed loop of fabric or webbing 60 may be mounted on suitable rollers (not illustrated) on the press frame to travel with the mash through the pressure zone 11 while upwardly closing the channel 28, as shown in FIG. 13c.

The solid conveyor plates 8, 8, 8" may be replaced by in terdigitated groups of bars 17, as is shown in FIg. 7, if the bars are heavy enough to withstand the pressure of the compressed mash. The ends of the bars are linked by hinge pins 18, and each group of bars thus constitutes a plate of the conveyor which may further be surfaced with a stainless steel sheet 21 in the manner discussed above with reference to FIG. 6. While apertured conveyor plates are not nonnally employed in the extraction of fruit juices in the presses of this invention, the presses may find applications in other fields where plates consisting of spaced rods or being otherwise apertured may be employed without covers impervious to liquid.

If the mash is relatively low in suspended solids, it may be desireable to remove a portion of the liquid before actual pressure treatment. FIGS. 8 and 9 show the front end of the apparatus of FIG. 1 to 3 together with a preliminary extracting device in a simplified manner, all supporting structure and other detail having been omitted for greater clarity.

Two roller conveyors 52 consisting of upright idler rollers 53 face each other and converge toward the entrance of the pressure zone 11. The guide pulleys 27, 27' are relocated near the wide end of the preliminary extraction zone 54 between the conveyors 52 to fold the web 23 into a U-shaped trough or channel which passes consecutively through the extraction zone 54 and the pressure zone 11. In the extraction zone, in which the pressure is relatively low, and not much greater than the hydrostatic pressure of the material confined in the web 23, the web can safely travel over the rollers 53 to extract much of the free liquid which drips through the web into a gutter 31-40 centered between the conveyors 52. Plastics or metal tubing may be used in making the rollers 53.

If the mash to be extracted is relatively low in moisture content, the arrangement partly illustrated in FIG. 12 has been found advantageous. The material is fed to the pressure zone 11 of a press otherwise identical with that shown in FIGS. 1 to 3 in three juxtaposed webs 23, 23 23" each of which is folded into a U-channel or trough at the entrance end of the press, and unfolded into a flat sheet at the discharge end by means of guide pulleys in a manner obvious from the preceding description, but not explicitly illustrated in FIG. 12. The porous material of the multiple webs provides ducts through which liquid may be discharged from the compressed solids in the press without diffusing to the sidewalls of the pressure zone.

While extraction presses for fruit juice normally have platens and webs which are upright, the invention is also applicable to extraction presses whose pressure zone is wider in a horizontal direction than it is high. Such a press is illustrated in FIG. 14. It is identical in most respects with the press described above with reference to FIGS. 1 to 3, but the shafts of the discs 6 are horizontal, and other spatial relationships are correspondingly changed.

The web is replaced by two continuous belts 50, SI of porous filter medium, such as canvas or wire netting, which are respectively superimposed on the plates of the two conveyors I in the pressure zone 11, thus leaving the zone open in both lateral directions for the discharge of juice into gutters not specifically shown. The material to be extracted is deposited on the lower belt 51 in an entrance zone 22 in which the belts 50, 51 converge relatively steeply toward the pressure zone.

Both conveyors 1 whose linear strands define the pressure zone of the presses described so far are plate conveyors, and substantially identical. Many advantages of this invention may also be derived from an extraction press in which only one of the two conveyors is a plate conveyor, as is evident from FIGS. 15 and l6.

The frame of the press consists mainly of two vertically spaced heavy plates 47 connected by tie rods 48 and fixedly mounted on a nonillustrated foundation. A cylindrical drum 35 is joumaled between the two plates, and its vertical shaft extends downward through the lower plate 47. Its projecting end carries a drive sprocket 6]. The aforedescribed discs 6 are rotated by means of similar sprockets, not shown in FIGS. 1-3. The sprocket 61 is connected with a nonillustrated electric drive motor by means of a link chain in a manner entirely conventional, and not shown for this reason.

An axially perforated flange 36 projects radially form the lower rim of the cylindrical surface of the drum 35, and a parallel imperforate flange 37 projects from the upper rim. The pressure zone ll of the press shown in FIGS. 15 and 16 extends in an are about the circumference of the drum 35 between the flanges 36, 37. The drum is covered in the zone 11 with a loop of filter canvas 38 which is also trained over an upright guide roller 40.

The outer wall of the pressure zone 11' is formed by a plate conveyor 1 closely similar to the conveyors I described above. The conveyor 1' consists mainly of hingedly connected plates 8 which travel over pins 9 on one pair of discs 6 and about approximately two-thirds of the circumference of the drum 35. The conveyor 1 is tensioned by a spring 7 acting on the bearings of the discs 6.

The conveyor 1 is backed in the pressure zone II by an arcuate row of rollers 19 mounted between the plates 47 and projecting into the space between the flanges 36, 37. They may be adjusted radially toward and away from the axis of the drum 35, as shown in FIG. 4. The surfaces of the plates 8 directed toward the drum 35 are covered by a loop of filter canvas 39 in the pressure zone 11, the canvas loop being trained over upright guide rollers 41, 42, 42' which lead it from the discharge end of the zone 11' to the entrance zone 22' of the latter.

The material to be extracted is fed to the entrance zone 22' and travels about the drum 35 between the canvas webs 38, 39 in the pressure zone 11 whose width decreases along the path of the material as the row of backing rollers 19' spirals toward the drum axis. The extracted juice flows downward by gravity between the yarns in the canvas webs 38, 39 and is ultimately discharged through the openings in the flange 36 into a circular gutter 46 under the drum from which it is further drained in a conventional manner.

The webs 38, 39 while traveling away from the drum 35, are reconditioned for again receiving mash by means of scrapers 43, rotary brushes 44, and water jets from spray nozzles 45.

What is claimed is:

I. An extraction apparatus comprising in combination a. two conveyors having respective endless faces, respective portions of said faces being oppositely spaced and defining therebetween a pressure zone, one of said conveyors including 1. a plurality of plate members having respective front and rear surfaces,

2. hinge means connecting said plate members into a closed loop,

3. guide means for guiding said one conveyor in a path in which from surfaces of said plate members are directed toward said guide means including a row of spaced pressure rollers engaging said rear surfaces,

4. a cover on each of said plate members and constituting the front surface thereof, said cover being impervious to liquid, and

5. cooperating sealing means on respective edges of each pair of adjacent plate members for sealing the covers on the members of said pair to each other while in said pressure zone;

b. drive means for during said conveyors for movement of said zone in a common direction,

1. the length of each of said plate members in said common direction being at least equal to the spacing of said backing rollers in said row, and

2. said rollers being positioned for continuously decreasing the width of said zone between said endless faces in said common direction; and

c. porous pliable web means for retaining coarse solids in said pressure zone while pennitting flow of liquid through said web means, said web means being superposed on each of said endless faces for movement with the same through said pressure zone.

2. An apparatus as set forth in claim 1, wherein said portions of said faces are upright and substantially impervious to liquid.

3. An apparatus as set forth in claim 1, wherein said plate members are of uniform length, and said drive means include a disc member having an axis, thereof, for rotating said disc member about the axis thereof and a plurality of abutment members axially projecting from said disc member in circumferentially spaced relationship, the spacing of said abutment members corresponding-to the unifonn length of said plate members, the loop of plate members being trained over said abutment members.

4. An apparatus as set forth in claim 1, wherein the spacing of said faces in said pressure zone varies in a plane perpendicular to said common direction.

5. An apparatus as set forth in claim 1, further comprising folding means and unfolding means, said web means including a web member forming a closed loop, said folding means folding said web member into a U-shaped channel prior to entry of the web member into said pressure zone, the leg portions of the U-shape respectively being superimposed on said front surfaces, and the bight portion of the U-shape closing said pressure zone between said faces, and said unfolding means flattening said U-shape after the web member leaves said pressure zone.

6. An apparatus as set forth in claim 5, further comprising means for closing the open side of said U-shaped channel.

7. An apparatus as set forth in claim 5, wherein said web member has two longitudinal edges and said folding means and unfolding means include guide means engaging said edges and guiding the same in respective paths, said paths extending along said pressure zone in said common direction in closely juxtaposed relationship, and diverging from each other in both directions away from said pressure zone.

8. An apparatus as set forth in claim 1, further comprising two rows of pressure rollers arranged spacedly opposite each other to define a preliminary extracting zone leading toward said pressure zone, said extracting zone tapering toward said pressure zone, said web means being superimposed on said pressure rollers in said extracting zone.

9. An apparatus as set forth in claim 1, yieldably resilient means biasing said backing rollers against movement outward of said pressure zone in the direction of the width of the latter.

10. An extraction apparatus comprising, in combination:

a. two conveyors having respective endless faces, respective portions of said faces being oppositely spaced and defining thcrebetween a pressure zone, one of said conveyors including 1. a plurality of plate members having respective front and rear surfaces,

2. hinge means connecting said plate members into a closed loop,

3. guide means for guiding said one conveyor in a path in which front surfaces of said plate members are directed toward said guide means including a row of spaced presure rollers engaging said rear surfaces;

drive means for driving said conveyors for movement of said zone in a common direction,

I. the length of each of said plate members in said common direction being at least equal to the spacing of said backing rollers in said row, and

2. said rollers being positioned for continuously decreasing the width of said zone between said endless faces in said common direction, 3. means for adjusting the width of said zone, said ad usting means including a cam member, a plurality of bearing supports movable in the direction of said width, said backing rollers being joumaled in said bearing supports respectively, said cam member simultaneously engaging said bearing supports, and means for moving said cam member; and

c. porous pliable web means for retaining coarse solids in said pressure zone while permitting flow of liquid through said web means, said web means being superposed on each of said endless faces for movement with the same through said pressure zone.

11. An apparatus as set forth in claim 1, wherein said portions of said faces extend horizontally, and said web means include two web members extending in respective closed loops and being respectively superimposed on said portions of said faces.

12. An apparatus as set forth in claim 1, wherein the conveyor is substantially identical with said one conveyor.

l3. An apparatus as set forth in claim 1, wherein the other conveyor includes a drum member having an upright axis, said endless face of said other conveyor including a cylindrical face of said drum member, said drive means rotating said drum member about the upright axis thereof, said other conveyor further comprising retaining means for securing said portion of said one conveyor in fixed axial relationship relative to said drum member.

14. An apparatus as set forth in claim 13, further comprising an apertured flange on said drum member, said flange downwardly bounding said pressure zone. 

1. An extraction apparatus comprising in combination a. two conveyors having respective endless faces, respective portions of said faces being oppositely spaced and defining therebetween a pressure zone, one of said conveyors including
 1. a plurality of plate members having respective front and rear surfaces,
 2. hinge means connecting said plate members into a closed loop,
 3. guide means for guiding said one conveyor in a path in which front surfaces of said plate members are directed toward said guide means including a row of spaced pressure rollers engaging said rear surfaces,
 4. a cover on each of said plate members and constituting the front surface thereof, said cover being impervious to liquid, and
 5. cooperating sealing means on respective edges of each pair of adjacent plate members for sealing the covers on the members of said pair to each other while in said pressure zone; b. drive means for driving said conveyors for movement of said zone in a common direction,
 1. the length of each of said plate members in said common direction being at least equal to the spacing of said backing rollers in said row, and
 2. said rollers being positioned for continuously decreasing the width of said zone between said endless faces in said common direction; and c. porous pliable web means for retaining coarse solids in said pressure zone while permitting flow of liquid through said web means, said web means being superposed on each of said endless faces for movement with the same through said pressure zone.
 2. said rollers being positioned for continuously decreasing the width of said zone between said endless faces in said common direction,
 2. hinge means connecting said plate members into a closed loop,
 2. hinge means connecting said plate members into a closed loop,
 2. said rollers being positioned for continuously decreasing the width of said zone between said endless faces in said common direction; and c. porous pliable web means for retaining coarse solids in said pressure zone while permitting flow of liquid through said web means, said web means being superposed on each of said endless faces for movement with the same through said pressure zone.
 2. An apparatus as set forth in claim 1, wherein said portions of said faces are upright and substantially impervious to liquid.
 3. An apparatus as set forth in claim 1, wherein said plate members are of uniform length, and said drive means include a disc member having an axis, means for rotating said disc member about the axis thereof, and a plurality of abutment members axially projecting from said disc member in circumferentially spaced relationship, the spacing of said abutment members corresponding to the uniform length of said plate members, the loop of plate members being trained over said abutment members.
 3. guide means for guiding said one conveyor in a path in which front surfaces of said plate members are directed toward said guide means including a row of spaced pressure rollers engaging said rear surfaces; b. drive means for driving said conveyors for movement of said zone in a common direction,
 3. means for adjusting the width of said zone, said adjusting means including a cam member, a plurality of bearing supports movable in the direction of said width, said backing rollers being journaled in said bearing supports respectively, said cam member simultaneously engaging said bearing supports, and means for moving said cam member; and c. porous pliable web means for retaining coarse solids in said pressure zone while permitting flow of liquid through said web means, said web means being superposed on each of said endless faces for movement with the same through said pressure zone.
 3. guide means for guiding said one conveyor in a path in which front surfaces of said plate members are directed toward said guide means including a row of spaced pressure rollers engaging said rear surfaces,
 4. a cover on each of said plate members and constituting the front surface thereof, said cover being impervious to liquid, and
 4. An apparatus as set forth in claim 1, wherein the spacing of said faces in said pressure zone varies in a plane perpendicular to said common direction.
 5. An apparatus as set forth in claim 1, further comprising folding means and unfolding means, said web means including a web member forming a closed loop, said folding means folding said web member into a U-shaped channel prior to entry of the web member into said pressure zone, the leg portions of the U-shape respectively being superimposed on said front surfaces, and the bight portion of the U-shape closing said pressure zone between said faces, and said unfolding means flattening said U-shape after the web member leaves said pressure zone.
 5. cooperating sealing means on respective edges of each pair of adjacent plate members for sealing the covers on the members of said pair to each other while in said pressure zone; b. drive means for driving said conveyors for movement of said zone in a common direction,
 6. An apparatus as set forth in claim 5, further comprising means for closing the open side of said U-shaped channel.
 7. An apparatus as set forth in claim 5, wherein said web member has two longitudinal edges and said folding means and unfolding means include guide means engaging said edges and guiding the same in respective paths, said paths extending along said pressure zone in said common direction in closely juxtaposed relationship, and diverGing from each other in both directions away from said pressure zone.
 8. An apparatus as set forth in claim 1, further comprising two rows of pressure rollers arranged spacedly opposite each other to define a preliminary extracting zone leading toward said pressure zone, said extracting zone tapering toward said pressure zone, said web means being superimposed on said pressure rollers in said extracting zone.
 9. An apparatus as set forth in claim 1, yieldably resilient means biasing said backing rollers against movement outward of said pressure zone in the direction of the width of the latter.
 10. An extraction apparatus comprising, in combination: a. two conveyors having respective endless faces, respective portions of said faces being oppositely spaced and defining therebetween a pressure zone, one of said conveyors including
 11. An apparatus as set forth in claim 1, wherein said portions of said faces extend horizontally, and said web means include two web members extending in respective closed loops and being respectively superimposed on said portions of said faces.
 12. An apparatus as set forth in claim 1, wherein the conveyor is substantially identical with said one conveyor.
 13. An apparatus as set forth in claim 1, wherein the other conveyor includes a drum member having an upright axis, said endless face of said other conveyor including a cylindrical face of said drum member, said drive means rotating said drum member about the upright axis thereof, said other conveyor further comprising retaining means for securing said portion of said one conveyor in fixed axial relationship relative to said drum member.
 14. An apparatus as set forth in claim 13, further comprising an apertured flange on said drum member, said flange downwardly bounding said pressure zone. 